Fibrous sheet material for the electrolytic formation of an azo dyestuff thereon



Patented Apr. 22, 194-7 FIBROUS SHEET MATERIAL FOR THE ELEC- TROLYTICFORMATION OF AN AZO DYE- STUFF THEREON Myer Solomon, deceased, late ofPrinceton, N. J

by Nellie W. Solomon, administratrix, Princeton, N. J., assignor toRadio Corporation of America, a corporation of Delaware No Drawing.Application December 23, 1942, Serial No. 469,957

'7 Claims.

This invention relates to the art of electrolytic dye production. Moreparticularly, it pertains to the production of azo and other dyes,embracing among its features novelty as to procedure, composition, andarticle of manufacture. In a preferred adaptation, it includes theproduction of dyes of the aforementioned type in connection with the artof facsimile recording. The fundamentals of the present disclosure areset forth in the copending application Serial No. 178,743, now U. S. P.2,306,471 included herein by reference, of which earlier application thepresent application is a continuation-in-part.

In the aforesaid copending application, there are disclosed applicantsgeneral methods of electrolytic dye formation designed particularly forelectrolytic recording, for example, facsimile recording. These methodscan be generally classified as, (I) electrolytic coupling, in which azodye formation is secured by first preparing a diazonium compound andsubjecting a solution of the diazonium compound together with a suitablecoupling compound to an electric current; (11) electrolyticdiazotization, in which a solution containing amine, nitrite, and acoupling compound is subjected to an electric current toelectrolytically form a diazonium compound andsecure the formation of anazo dye by the coupling of the diazonium compound with the couplingcompound during the action of the electric current, after its action, orboth during and after; and (Ill) electrolytic oxidation, in which dyesare formed by electrolytically oxidizing chemicals that react to producedyes, either exclusively or conjointly with method (II) Thus, variousdifferent types of facsimile receivers are used at the present time, andin substantially all of them pictures, printed matter, or othercharacters are produced on a recording sheet of paper in response tovariations in electrical current which are received from the transmitterstation. In one type the reproduction of the character or indicia isthrough the use of carbon paper and the transfer of the carbon to therecord paper is accomplished by means of an electromagneticallycontrolled printer bar. In such a device the recording paper and carbonpaper are placed in the facsimile receiver and are moved forward at ratewhich are necessarily' slow because of mechanical inertia limitations,while line increments of the material being received are reproducedthrough the application of varying degrees of pressure to the printerbar, in order that varyin amounts of the carbon will be transferred fromthe carbon paper to the recording paper. Such a device for facsimilerecording is shown in the patent to Charles J. Young, Reissue #20,l52',October 27, 1936,

In another type, a light sensitive recording paper is used and theamount of light permitted 2 to strike the paper is controlled inaccordance with the electrical variations transmitted by the facsimiletransmitting device. In this type some developing or fixing processgenerally follows.

In still another type a stream of hot air is directed against a heatresponsive recording paper, the intensity of the heat or the amount ofhot air being controlled in response to the energy transmitted by thefacsimile transmitting device. Another type uses a jet of ink or somecolored fluid, the jet being permitted to strike, or prevented fromstriking, the recording paper according to the series of signalsreceived from the transmitting device. The patent to Richard H. Ranger,#1,'l70,493, of July 15, 1930, shows, for example, devices wherein jetsof hot air or ink are used for facsimile recording.

In the facsimilie receiving or recording systems referred to above, theproduction of half tones and shades such as occur in the reproduction ofpictures, is somewhat difiicult, since, for instance, in the carbonpaper method, the transfer of the carbon to the recording paper issomewhat critical in response to the pressure applied to the printerbar. Furthermore, the use of hot air or ink jets is not entirelysatisfactory sincesuch systems are diificult to control and to maintainin proper operation.

The present invention may be generally characterized as directed to dyeformation, in which electrolytic action plays an essential part, and isparticularly applicable to the electrolytic diazotization method (II)above while utilizing heterocyclic amines for forming the diazoniumcompound.

It is an object of the invention to overcome the difficulties andlimitations of the prior art procedures noted hereinabove.

It is another object of the present invention to obtain diazoniumcompounds by the action of an electric current on mixtures or solutionscon-' taining diazotizable heterocyclic amines and nitrites.

It is a further object to provide mixtures or solutions containingdiazotizable heterocyclic amines and nitrites which are adapted toelectrolytically react for the purpose of producing diazonium compounds.

Another object of the invention is to provide solutions or, wherefeasible, mixtures, of appropriate reagents comprising a diazotizableheterocyclicamine and an ionizable nitrite which are adapted forelectrolytic reaction to produce a diazonium compound, and to form azodyes from such diazonium compound by reaction with a coupling reagentpresent in said mixture or solution.

An added object of the invention is a supporting material or carriertreated with azo dye forming chemical reagents including a diazotizableheterocyclic amine which willreact suitably when subjected toelectrolytic treatment, said carrier as a result of its chemicaltreatment being electrolytically conductive.

A still further object of the invention is to provide a supportingsurface Or carrier which is saturated or impregnated with a diazotizableheterocyclio amine and an ionizable nitrite, which is advantageouslyadapted for production in situ of a diazonium compound when subjected toan electric current.

An additional object of the invention is to p ovide a supporting surfacesaturated or impregnated with a diazotizable heterocyclic amine, anionizable nitrite, a coupling reagent, an electrolyte, said supportingsurface being thereby adapted for electrolytic facsimile recordingthrough azo dye formation.

Another object of the invention is to provide suitable procedures forpreparing the compositions and articles of manufacture hereinabovereferred to.

Other objects, features and advantages of the invention Will'be apparentfrom the following detailed description.

In the present invention, it is proposed to produce the picture orprinted matter on the recording paper in the form of a dye, the amountof such dye deposited being a function of the amount of current causedto flow through the recordingpal er. When the image is thus formed, forexample, by applicants electrolytic azo dye formation, the pressure ofthe printer bar can be maintained constant and the amount of currentwhich is passed through increments of the paper simply varied inaccordance with the light and d'ark' portions present on the picture orprinted matter being scanned at the facsimile transmitter. When dyes areso formed by electrolytic action, the varying half tone shades may beproduced by merely regulating, the amount of the current which is causedto fiow through the recording paper.

The principle of operation of the present invention depends. on the factthat when an electric current flows through a mildly alkaline solutioncontaining a suitable diazotizable heterocyclic-amine, and a source ofnitrite ions a diazonium compound is formed at the acid or positiveelectrode termed the anode. Said diazonium compound is capable ofcoupling with an azo dye coupling component. to produce. an azo dye.Saidoperation employs as essential components the following:

(a) A heterocyclic amine, desirably a primary amine.

' (b) A nitrite.

() An alkali.

(d) A coupling compound.

(e) An electrolyte.

(f) Water orother Solvent in which electrolytes ionize.

Among the amines which may be utilized are heterocyclic amines with anuclear attached p'rimary-amino group such as the amino quinolines,amino pyridines and amino pyrimidines uch as 2.6-diamino pyridine. Thepresence of a sulphonate group tends to enhance the stability of thebackground of the carrier towards light although the dye may, in somecases, manifest somewhat less fastness to washing.

The following coupling compounds may be utilized for forming the azodyestuffs electrolytically while utilizing the aforementioneddiazotizable heterocyclic amines.

Benzene compounds Resorcinol '41-chlororesorcinol 2 -nitroresorcinol.

Sal'icylaldehyde Salicylaldoxime 5-chlorosalicylaldehyde5-chlorosa1icylaldox-ime OrthohydroxybenzalacetophenoneOrthohydroxybenzalacetophenoneoxime -oH=oH-( NOH ResorcylaldehydeResorcylaldoxime Resorcylic acid Parahydroxyacetophenone-Parahydroxypropiophenone Resacetophenone. ResacetophenoneoximePhloroglucinol Metaaminophenol AcetoacetanilideIsonitroscacetoacetanilide IsonitrosoacetoacetanilideoximeAcetoacetanilideoxime- Acetoacetanilide hydrazone'2-ch1oroacetoacetani1ide- 2-chl-o-ro-isonitrosoacetoacetanilide2,5-dichloroacetoacetanilide 2,5-dichloro-isonitrosoacetanilideAcetoacetanilide-parasulphonic acid Acetoacetanilide oxime parasulphonicacid' l-metaarninophenyl-3-carboxy-5-pyrazolone Hydroxylamine with No.112 Acetoaceta-nilide hydrazone para-sulphonic'acldOrthopheny-lenediamine Metaphenylenediamine ParaphenylenediamineChloroparaphenylenediaminedihydrochloride 2,5-diaminobenzenesulphonicacid" dihydrochloride Diacetoacetyl-paraphenylenediamineDiisonitrosodiacetoacetyl-paraphenylenediamineDiacet-oacetyl-paraphenylenediaminedioxime ZA-diaminotoluene2,5-diaminotoluenedihydro'chloride 2,4-diaminoanisoledihydrochloride.2,5-diaminoanisoledihydrochloride Triaminotoluenetrihydrochloride4,4-dihydroxybenzophenone' 4,4-dihydroxybenzophenoneoximeMetadiethylaminophenol Metadigallic acid (tannic acid) Naphthalenecompounds Alpha naphthol Alpha hydroxynaphthoic acid Schaefiersalphanaphtholsulphonic salt Neville and Winthers acid L acid N-phenylperi acid RG acid' Andresens acid Schoellkopfs acid Oxy Koch acid Betanaphthol Beta hydroxynaphthoic acid Naphthanil OA' Schaefiers acid E-salt '5 Bayers or Crocein salt Disodium R salt Disodium G saltNaphthoresorcinol 1,5-dihydroxynaphtha1ene 1,7-dihydroxynaphthalene-4-sulphonic acid Dioxy S acid Nigrotic acid Yellowacid Red acid A acid Chromotropic salt or acid 2,7-dihydroxynaphthalenePhenyl J acid Benzoyl J acid Di J acid urea J acid Imide J acid M acidGamma acid Phenyl gamma acid S acid Chicago or 28 acid Monosodium H saltChloro H acid Phenyl H acid Acetyl H acid K acid 2R acid (oxyamino) Racid (oxyamino) Miscellaneous compounds 8-hydroxyquinoline8-hydroxyquinoline-5-su1phonic acid Barbituric acid Violuric acidI-Iydroxylamine with 179 Thiobarbituric acid Th'iovioluric acid1-phenyl-3-methyl-5-pyrazolone 1-parasulphophenyl-3-methyl-5-pyrazoloneHydroxylamine with 185 l-parasulphophenyl-3-carboxy-5-pyrazolone2,6-diaminopyridine DiacetoacetylethylenediamineMonoisonitrosodiacetoacetylethylenediamineDiisonitrosodiacetoacetylethylenediamineMonoisonitrosodiacetoacetylethylenediamineoximeMonoisonitrosodiacetoacetylethylenediaminedioximeDiisonitrosodiacetoacetylethylenediamineoximeDiisonitrosodiacetoacetylethylenediaminedioxime Relative to theproportioning of the ingredients, as a general rule by way of estimateand not restriction, approximately 0.03 gram molecular weights (0.015for diamines) of amine and of a monovalent nitrite per liter of solutionproduce quite satisfactory results. Usually 0.025 gram molecular weightsor mols of amine are used per liter of solution for paper that istreated at the recorderthat is, for paper which is subjected to thediazotizable solution substantially at the time that the recording ismade.

A comparatively wide range of nitrites are available, the requisitebeing an ionizable compound, desirably a metallic nitrite. Whereas theexamples in the present disclosure may largely involve the use of sodiumnitrite, it should be clear that this compound is referred to merely asillustrative of a convenient material which may be utilized in thediazotization procedure. While sodium provides entirely satisfactoryresults, the same may be said of potassium nitrite as well as many-othermetallic nitrltes. In view of the fact that neutral or alkalinesolutions of sodium ni trite are comparatively stable, this reagent isparticularly desirable in predetermined recording solutions prepared forstorage over a substantial period prior to usage. It has been found thatexcess nitrite does not impair the background permanence of electrolyticdiazotization recordings and is in fact beneficial because it causes agreater percentage of the amine to be diazotized, and consequentlypermits a decrease in th concentration of amine with no loss in colorintensity. Concentrations of 0.025 and 0.05 gram molecular weights ofamine and of nitrite, respectively, per 1000 cc. of solution, usuallygiv excellent results.

Similarly, a substantial'latitude in choice of alkaline reagent isavailable, but for purposes of illustration herein, recourse is had tosodium hydroxide. The usual content of sodium hydroxide may becharacterized as that required to new tralize all strongly acid groupsin the amines and coupling compounds, as well as that providing a slightexcess (usually 20 cc. of normal NaOI-I per liter or recordingsolution).

Where the alkalinity pertains to the recording solution and is notparticularly critical, simple expedients for its approximate evaluationare available in the form of the so-called Beckman instrument or othercommercial devices. Similarly, a small piece of La Motte Oleo Red 13 pHtest paper may be immersed in the facsimile record: ing solution for afew seconds. The alkalinity is satisfactory if the paper turnsorange-brown, insufiicient if yellow or orange-yellow, and excessive ifred. It should be noted that insufficient alkalinity is more harmfulthan excessive, since it impairs the background permanence; on the otherhand, a stronger signal in the form of electrical impulse is requiredfrom the amplifier, and half tones are impaired, when the solution isexcessively alkaline.

As a general matter, the color intensity at full electric currentdepends on the alkalinity and the amount of diazonium compound formed.The deepest color is usually formed at a pH of 7.5 to 9 which is notalkaline enough for good background permanence. At a pH of.6 to 7.5,hydroxy coupling is too slow in some cases, and prematurenon-electrolytic diazotization discolors th paper in others. At thecompromise pH range of 9 to 11.5, the color intensity is not sacrificedunduly in order to gain in background permanence.

Insofar as th diazotizable composition and the treated carrier, such aspaper, are concerned, they may be stored a considerable period of timeif the solution is moderately strongly alkaline. A pH range of 7.5 to12.5 is applicable, although best results are obtained within the rangeof 10.0 and 11.5. As the pH drops, the stability decreases, the tendencyof the background to darken on standing increases, and the sensitivityof the reaction increases.

In lieu of sodium hydroxide, oth'er strong bases may be used, asillustrated by potassium hydroxide, barium hydroxide, or a quaternaryammonium hydroxide. On a weight basis, the amount of alkali used mayvary from 0.01 to 0.12 gram molecular weights per liter of solution,depending upon the original acidity or alkalinity of the otheringredients, and is adjusted to the predetermined pH of the finishedsolution, which, as above suggested, may desirably be within the rangeof 10.0 to 11.5.

Concerning the coupling compounds, herein above they are desirablysoluble in a mildly alka.-

line salt solution and preferably subject to the same oxidationlimitations as discussed above in connection with the amines. Aromaticcompounds with hydroxy, amino or. active methylene groups ortho or parato unsubstituted positions in the ring will usually couple- Sulphonicgroups have the same effect as in amines. Resorcinol, phloroglucinol,thenaphthols and their sulphonic acids, 8-hydroxy quinoline, and someamino naphthol sulphonic acids have given good results. Some aminonaphthol sulphonic acids (for example, gamma, H, J, S and 2S acids) mayeither diazotize or couple. Good recordings may thus be obtained, usingthe same chemical for both diazotization and coupling. However, mostamino-naphthol sulphonic acids give recordings that require washing inorder to prevent the backgrounds from darkening during storage.

Chromotropic salt is considered the best. allround coupling compound,giving darker colors than any of the others having reasonably permanentwhite backgrounds. The acetoacetylamino compounds, their oximes andhydrazones, and the isoxazolones and pyrazolones derived from them, giveyellow or orange colors, the oximes and hydrazones being most effective.When added to facsimile recording solutions containing chromotropicsalt, these yellow or orange couplers improve the color, givingbrownish-purple shades that are more pleasing in appearance than thepurple obtained with chromotropic salt alone. The ratio of chromotropicsalt to oxime or hydrazone is usually three gram-molecules to one.

The coupling compounds may be utilized individually or in admixture,particularly desirable results being obtainable from the use of aplurality of coupling compounds, as indicated in an example hereinbelow.

The amount of coupling compound utilized may vary between 0.01 to 0.02gram molecular weights, although more may be utilized without harm.Usually approximately 0.015 gram molecular weights of coupling compoundper liter of solution provides excellent results, and a greater amountrarely shows any improvement in recorded color intensity.

The coupling compound may be of the type which reacts in alkaline mediumor in acid medium, although the former is preferable. It is interestingto note that some amino compounds may function as coupling agentsregardless of the pH, and many diazotizable primary amines serve in thedual function of amine and-coupling compound. Under alkaline conditions,the hydroxy-coupling rate of reaction is generally so much greater thanthe amino coupling rate that substantially little or no amino couplingtakes place in alkaline solution when both amino and hydroxy groups arepresent.

As for the electrolyte (e), NaCl-is quite satisfactory, but there is nointent to be limited to the use of this salt. Other strong watersoluble, inorganic salt electrolytes such as NaBr, KBr, KCl, LiCl,BaClz, CaClz, MgCla, K2SO4, Nazsoi, MgSO4, etc., may be substituted forsodiumchloride. Some dye intermediates are more soluble in potassiumchloride solutions, in which cases the substitution is made. Lithiumchloride has been found to retard the time of paper drying, but the sameresult is cheaper and more effectively obtained by the use of wettingagents. An additional electrolyte which hasprovided excellentrecordings, while at the same time obviating the corrosive effect ofnascent. chlorine, is sodium sulphamate, NaOSOzNI-Iz.

. and recording generally.

The amount of electrolyte required is not critical. Low concentrationsrequire more electric current, while excessively high concentrations maycause partial precipitation of the dye intermediates. About two-thirdsof a mol (a mol equals one gram molecular weight) of total electrolyteper liter of solution is fully adequate. For convenience in making thesodium ion correction to the Beckman pH meter readings, a total sodiumion concentration of 0.64'mol is used. The total sodium present in allthe other ingredients is subtracted from 0.64, the remainderrepresenting the amount of sodium chloride to be added.

Where NaCl is utilized, it has been found that the total concentrationof sodium ions equal to 1.0 gram molecular weights per liter is quiteeffective, although good recordings have been obtained in some caseswith as low as 0.1 and as high as 3.0 gram molecular weights of sodiumper liter.

Substitution of sodium oxalate for part of the sodium chloride retardsthe background darkening of damp pretreated paper, although the electriccurrent requirements are increased, and the halftone response issomewhat impaired. Oxalates have little effect on the backgroundpermanence of recordings exposed to light after drying, and their use isadvisable primarily with damp treated paper.

It is, of course, apparent that water functions as a very desirable andeffective vehicle within which the diazotization and azo dye formationare carried out. However, various non-aqueous neutral solvents thatpermit electrolytes to ionize may be substituted for all or a part ofthe water. If approximately half the water is replaced by alcohols orglycols, the freezing point of the solution is lowered to such an extentthat recorders may be operated outdoors in-winter.

Ethyl, methyl and isopropyl alcohols evaporate more rapidly than water,so that the paper dries too quickly'in summer; in winter the added speedis desirable. Normal propyl alcohol dries at approximately the same rateas water, and may be used both summer and winter; the tendency of thepropanol-water-salt mixture to separate into two liquid phases isefiminated by replacing ten per cent of the propanol with ethyleneglycol. Larger amounts of the glycols are unsatisfactory, as their lowvolatility causes the recordings to be permanently limp and moist.

Some solvents, notably Cellosolve, methyl Cellosolve, and most denaturedethyl alcohols, gradually react with the alkali in the recordingsolution, which eventually becomes acid (unless more alkali isoccasionally added), whereupon diazotization and coupling begin, causingpaper treated with the solution to become discolored. Normal propylalcohol and ethylene glycol do not reduce the alkalinity.

It will be noted that auxiliary chemicals are of substantial usage, andcontribute materially to the control of the diazotization, dyeformation, Such substances as oxalates, antifreeze solvents,hydroxylamine and hydrazine may be considered either as auxiliarychemicalor as replacements for part of the essential chemicals.

An important role may be attachedto the use of auxiliary chemicals inconnection with the dye formation, and particularly where facsimilerecording is concerned. These substances contribute materially to thecontrol of the diazotization, dye-formation, and recording generally.

Urea, thiourea, and, to a still greater extent, dicyandiamidine havebeen found to improve the color intensity. About 1 to 2 mols of eitherof these compounds per mol of amine are used. This effect is moreapparent when combined with that due to excess nitrite. If a sulphate orhydrochloride of these bases is used, sufficient caustic sodaor otheralkali must be added to liberate the free base, in order to maintain theproper pH range.

Providing a desirable function in connection with recordings, wettingagents may be utilized in the treatment of the carrier, such as paper.Many of such wetting agents and their general field of usage as well aschemical characteristics are set forth in the,Journal of Industrial andEngineering Chemistry, volume 31, June 1939, pages 66-69. Wetting agentswhich have been found quite effective are those sold under the trad nameTriton 812 and Triton 720, which are understood to be sulfonated,polyalkoxylated aryl compounds, and Aerosol OT, which is dioctyl sodiumsulfo succinate.

The rate of penetration of the dye forming solution into the carrier orsupporting material, such as paper, is most rapid at high alkalinity andlow surface tension of the solution, as well as at high atmospherichumidity. It is in this connection that wetting agents have been foundhighly effective in reducing the surface tension sufficiently foradequate wetting to occur in a brief interval of paper submersion time,desirably approximately six seconds, regardless of the humidity andalkalinity prevailing. As an example of the quantity of Wetting agent,0.8 gram of wetting agent solids per liter of solution have been foundto afford adequate wetting when the paper is immersed; where the paperis supplied with the dye forming solution through the expedient ofcontact with a wet roller on one side alone, approximately 1.5 grams ofwetting agent per liter of solution may be essential.

The desirability of resort to wetting agents in the recording solutionsis emphasized by the fact that without the same it has been necessary tosubmerge the paper for at least two minutes to insure adequate wettingon dry days. The use of pretreated paper, i. e., paper treated withrecording solution prior to its utilization in the recording apparatus,has heretofore proven impractical for the electrolytic treatment whensubjected to moistening by water in the absence of a Wetting agent.Differently stated, the wetting agent causes the water to penetratepretreated paper more rapidly than the solution penetrate-s untreatedpaper. Moreover, an additional function of the wetting agent is to causethe recording solution on the surface of the paper to continuepenetration until saturation occurs, where excess liquid is available onthe paper surfiace.

At that time, any remaining excess of liquid is subject to removal inaccordance with any conventional expedient, such as by resort to adoctor blade or to a preheater.

An undue amount of liquid on the paper may function to cause blurring atthe instant of printing. Where the interval between paper wetting andfacsimile printing is comparatively long, the tendency is for the paperto become partially dry, causing streaking and paper scumng when theprinting is applied. The wetting agents, under these circumstances,serve to retard the rate of drying at this stage of the operation.Glycols and other high boiling solvents also retard drying .at roomtemperature and improve wetting, but

they are not as effective as wetting agents, there by necessitating muchgreater concentrations- If the damp paper, after being subjected torecording, is passed over a hot roller for the purpose of drying andironing it, the glycols require a greater extent of heating, since athigher temperatures they are more effective than wetting agents asdrying retardants. Wetting agents similarly are advantageous in the caseof pretreated damp paper which is stored in a moistureproof container,to be later positioned in a slotted container at the point of unrollingat the recorder.

The color intensity at full electric current is aifected by thealkalinity and the amount of diazonium compound formed. The deepestcolor is usually obtained at a pH of 7.5 to 9, which. may not besufficiently alkaline for optimum background permanence. At a pH of 6 to7.5, hydroxy couplin is too slow in many cases, and p'rema turenon-electrolytic diazotization may discolor the paper in other cases. Byresort to'the compromise pH range of 9 to 11.5, the color intensity isnot materially sacrificed, and at the same time background permanence isattained.

The effect of urea, thiourea and dicyandiamidine as reagents forimproving color intensity has been amply treated, hereinabove.

An additional element which materially affects" color intensity is theamount of diazonium compound formed electrolytically. It will beaDDreciated, in this respect, that the halftones of photographs arereproduced by variations in color intensity caused by variations insignal strength. The extent of diazonium compound formation, andtherefore color intensity, assumes the characteristics of a linearfunction of the current flow, except at very low currents where thecolor intensity drops sharply due to the so-called threshold valueeffect. In view thereof, reducing agents as well as high alkalinityserve to detract from the light tones. This threshold effect-may becompensated by resort to color-deepening chemicals, illustrated by urea,thiourea, and dicyandiamidine, which improve the halftonecharacteristics by accentuating the light tones.

Other substances which tend to deepen the color or improve backgroundpermanency 'are bari'um and calcium chlorides which may be substitutedin part, or entirely, for sodium chloride as the electrolyte. Suchsubstitution may, however, not be without its shortcomings in view ofthe possibility that the solubility of the dye chemicals may be loweredand on occasion objectionable sludges may be formed.

Through the choice of primary amines and 'coupling compounds used agreat variety of colors may be obtained, although orange, red and purpleshades predominate. In general, the orange dyes give recordings whosebackgrounds are more permanent without washing than the reds, purples orblues. Furthermore, it has been found that alpha-naphthalene compoundsgenerally give darker colors, but with less permanent backgrounds, thanthe corresponding beta compounds.

On the question of background permanence, some amines and couplingcompounds, in some cases those having two or more amino or hydroxygroups on the same benzene or naphthalene ring, may manifest an unduetendency to air oxidation; in view thereof, it may be desirable as ageneral expedient to wash recordings made through the use of suchreagents within a few hours after such recordings in order to preventexcessive background darkening on storage. Taken as a whole,

the remaining amines and coupling compounds give satisfactory recordingswhich retain their white backgrounds, or at least do not darkensufiiciently to impair their legibility and utility when stored severalyears in a file or holder.

As previously suggested, various chemicals function to retard backgrounddarkening, among whichare the glycols; these substances are used in theproportion of approximately 100 cc. per liter of solution. In somecases, they reduce darkening due to the slow reaction during storage,but are not as effective with respect to darkening which results fromlight exposure. Reducing agents, such as sodium hydrosulphite(Na2S204.2I-IzO) andacetaldehyde sodium bisulphite (NaOSOaCHOI-ICHa)tend to retard the darkening action of light, but may not preclude slowdarkening. Quantities varying from 0.002 to 0.01 mol per liter have beenutilized with effective results within the scope indicated. The reducingagents specified are merely illustrative, since other reducing agentshave a similar effect. Such other reagents are tartrates, formates,sulphites, thiosulphites, other hydrosulphites than "sodium, mentionedabove, etc.

The effect of alkalinity upon background darkening has already beenrecited, and the same applies to the optimum range of pH between 9.5 and11.0, especially where sodium chloride is used as the electrolyte.Higher pH may cause weakening and decomposition of the paper, whilelower pH may result in partial oxidation and partial selfdiazotizationof the amines. The pH of the paper before treatment with the solution isknown to effect the final alkalinity of the treated paper; therefore, ifan acid paper is used, the alkalinity of the solution should beincreased to compensate therefor.

Complex cyanides of iron, chromium, or other metals, in some instancesimprove the fastness of the dye to washing and deepen the shade, or evenalter the dye color. Noteworthy is the fact that dyes are on the wholedistinctly faster to washing than the intermediates from which they areformed; as a result of this, washing may be resorted to for removingunused chemicals from the unrecorded areas, thereby leaving the dyesintact,-correspon ding to the subejct-of transmittal. .-As ageneralrule, recordings intendedto be washed should preferably be made at a pHrange of 8.0 to 10.0 within the broader range of 9 to 11.5; in this wayadvantage is taken of the greater color strength and increased fastnessduring such pH range. Urea, thiourea, and dicyandiamidine increase thefastness to washing. Thus these compounds serve thedual function ofimproving color strength as well as color fastness.

The minimum current which is required to produce a faint color isreferred to as the threshold value. Before diazotization can take place,the initial alkalinity of the wet paper must be overcome. If reducingagents are present they are oxidized by part of the current, leavingless for acidification and diazctization. Thus the reducing agentsreferred to hereinabove show this threshold value effect. With neutralsolutions or in the absence of reducing agents, small stray currentscause streaks and spots of color on unrecorded areas, thereby detractingfrom the appearance of the recordings and in some cases seriouslyinterfering with the legibility of the small type.

The application of a constant negative potential to the printingmechanism has an effect analogous to that of high alkalinity inpreventing streaks due to stray currents, since the positive facsimilesignals must overcome this negative voltage before color appears. Thisexpedient is, however, not without some difficulties in the way of anincreased rate of corrosion of the negative electrode, and in the caseof certain metals produces a pale negative recording on the back of thepaper. It may also tend to eliminate the lighter shades in reproductionof photographs.

Illustrative of desirable embodiments of the invention, the followingexamples are presented:

Example 1 Mols per Grams per 250 Name and Use Liter Liters Pre-il fircedIngredients Benzldinc-3-3-disulphonic Acid .015 1,634.5

(amine). Acctoacctanilide (coupler) .002 88.5. Ecliaefiers Salt(coupler) .003 231.0. (lilromotropic Salt (coupler) .010 1,248.7. SodiumHydrosulphite (aux .003 157.5. Urea (auxiliary) .010 150.2. SodiumChloride (electrolyte) .450 6,576.1

Separate Mixture Sodium Hydroxide (alkali) 061 6210.6 or 0.10

1 rs. Sodium Nitrite (nitrite) .060 1,035.2 or 3.00

iters. Triton 720 (wetting agent) 08% 750 cc.

Example 2 Mols per Grams per Name liter Liter Pre-Mz'xed IngredientsBcnZidine-B,3-disulphonic Acid .015 6.558. Ohromotropic Salt .015 0.000.Barbituric Acid .004 0.512. Sodium Hydrosulphite .0028 0.588.Dicyandiamidino Sulphate 0010 0.316. Thiourea .0010 0.07 6'. SodiumCarbonate .030 3.721. Sodium Chloride .300 17.530.

Separate J'Vfilture Sodium Hydroxide 2.5 Normal .050 20.0 Sodium Nitrite5.0 Molal .074 14. 8

It will be noted in the above examples that while the ingredients ineach instance are separated into two groups, this is primarilyindicative of a desirable expedient for packaging or storing thereagents ,prior to usage. However, considering the compositions from thestandpoint of their substantive content, they comprise the reagentsspecified in both groups.

As illustrative of the preparation of the composition of Example 1, theproper amounts of each of the pre-mixed ingredients are weighed, and allare thoroughly mixed mechanically. A convenient method utilizes aninclined rotating drum containing pebbles or metal balls to break up any.lumps in the chemicals. The mixture may be stored in bulk or packagedin small packages each containing the required quantity for a quart,liter, gallon, or other desired volume of recording solution.

Since measuring liquids is much more convenient than weighing solids, itis advisable to use concentrated stock solutions of sodium hydroxide andsodium nitrite instead of'the corresponding solids. Approximately 2.5normal sodium hysodium nitrite (345 grams per liter) are adequate.

The wetting agent is already in liquid form.

Irrespective of the predetermined coloration to be obtained, dependentupon the reagents utilized, the supporting material, such as the paper,after haVing been appropriately treated with the reagents, is passedthrough the facsimile recorder in wet or moist condition. Adesirablefacsimile recorder which may be utilized is the bar-helix type, the barserving as the anode and the helix providing the cathode. However, it isapparent that the performance of the recording is not restricted to theuse of any particular type of apparatus.

Upon contact with the printing electrodes of the recorder, the diazoniumcompound is formed, which couples with the coupling component present.As previously indicated, the operation is not restricted to the use ofany particular recording device, and may be adapted to any of thoseknown to the prior art, Desirably, the treated or sensitized paper isfed continuously from a roll; where the paper has not been sensitized,it is initially fed from the roll through the appropriate immersion bathfrom impregnation with the dye intermediates and auxiliary compounds,the excess immersion solution removed, and the paper passed directly tothe recorder.

The reference to paper as the supporting material or carrier has beenrecited solely by way of illustration. Substantially any fibrousmaterial capable of being dyed by an azo compound is withincontemplation, including such materials as fabric, cloth, and othertypes of cellulosic sheets, regenerated or otherwise. Quite desirableresults have been obtained with an all-rag sheet,

surface-sized with glue-formaldehyde in order to impart adequate wetstrength. Similarly, good results have been obtained with partiallyparchmentized wood pulp paper. In the case of papers which are toohighly sized, wetting agents are satisfactorily employed to facilitatequick penetration of the solution; from 0.5 to 1.5 grams of wettingagent solids per liter of recording solution is usually sufficient forthis purpose. Among the effects produced are more rapid solutionpenetration into the paper and" slower drying after leaving the treatingbath.

Most all-sulphite papers are too weak when wet to be used onelectrolytic b'ar-and-helix facsimile recorders. When treated withurea-formaldehyde resins, sulphite paper increases in wet strength tothe point where it becomes usable,

although the tendency of formaldehyde to combine With the amine beforediazotization weakens the recorded color, If a sulphite with a fairlyhigh initial wet strength is used, a moderate treatment gives adequatestrength without excessive color-weakening. The treatment is preferablyapplied to the unsized paper.

Effective results may be obtained by combining formaldehyde and ureawith the recording solution which has been freshly prepared, whenglycols are also included to stabilize the initial resins formed.However, such solutions are not particularly stable when retained instorage for several days, since a substantial proportion of the aminecontent is consumed, thereby resulting in a decrease in recorded colorintensity, Freshly prepared solutions of this type utilized in obtainingdry pretreated paper (paper which has been treated with the reagentsolution and dried preliminary to its utilization as a recording sheet)may set the resin, and the dry storage condi- 14 tions serve to preventor minimize the relatively slow chemical reaction between theformaldehyde resin and the amine.

After subjecting the sheet to electrolytic treatment, especially wherefacsimile recording is involved, the carrier in a dry state is desirablykept in a folder protected from exposure to light, Al though there maybe a slight decoloration of the background after several hours exposureto daylight, this does not seriously affect the utility of the article.Washing the freshly recorded sheets thoroughly with water at the mostonly slightly weakens the coloring of the dye which has been formed; atthe same time, such washing substantially improves the permanence of thebackground.

Under preferred conditions of operation, the recording paper, afterhaving passed through the facsimile receiver with the azo dye. formedthereon corresponding to the subject-matter scanned at the transmitter,the supporting paper may be subjected to a fixing bath for the purposeof rendering the dye more permanent in nature and/or to aid in thepreservation of the White or neutral characteristic of the background,Pursuant to such fixation, the paper is then desirably washed, as aboveindicated, to remove any chemicals which remain in the undiazotizedportions of the paper in order to thereby minimize any tendency towardgradual fading of the color produced or darkening of the background whenthe recorded copy is exposed to light and/or air.

In preparing the various reagent solutions for utilization to saturateor impregnate the supporting material, certain precautions and detailsof procedure may be advisable, dependent upon the particularcircumstances involved. Thus, where all the ingredients of a solutionare neutral or alkaline upon their being dissolved in water, they mayall be dissolved together. The sodium and potassium salts of aminoo-rhydroxy-naphthalene sulphonic acids fall in this class. Where theamines, coupling compounds, or other ingredients are free acids asdistinguished from sodium or potassium salts, it is necessary to omitthe sodium nitrite from the solution until all the acidic compounds havebeen dissolved by the excess alkali required to give the roper finalalkalinity. Failure to observe this precaution results in the formationof diazonium compounds in the acidic zone adjacent to each dissolvingcrystal of the acidic compounds, with subsequent coupling and dyeformation when the diazonium compound has reached the alkaline zone.Such solutions discolor any paper that is treated with them.

On storage, the solutions may tend to darken because of auto-oxidationof some of the ingredients, especially if exposed to light in clearbottles and to air in partly emptied bottles; sometimes this oxidationcauses the formation of sediment, even though the solution wasoriginally filtered. Nevertheless, good recordings have been obtainedwith some year-old solutions, at a slight sacrifice in backgroundpermanence. Solutions that have become dark on standin may be restoredto their original color (amber, clear brown,

or red) by the addition of small amounts of storage is avoided, sincesalt is inert with respect to the other ingredients. In case any of thedry solids cake in the container, they may be rinsed into the solutionwith water.

In packagin the reagents in admixture and in their dry state,precautions similar to those above suggested are essential; thus, it isnecessary to omit the sodium nitrite from packages wherein the reagentsmanifest free acidity. After thedry reagents are dissolved and theappropriate content of alkali has been added, the nitrite may then besupplied. In this manner, premature dye formation is avoided.

As a convenient expedient, large batches of all of the dry materialsother than sodium hydroxide and sodium nitrite, may be mixed thoroughlyand subsequently stored indefinitely. Recording solutions are preparedfrom such mixtures by dissolving Weighed or measured amounts of the drymixture in water containing a weighed or meas ured amount of sodiumhydroxide, and subsequently adding the proper quantity of sodiumnitrite, more water to the required volume, and wetting agent if needed.Sediment i removed either by filtration, decantation after settling, orby a combination of both methods.

In preparing the carrier material, illustrated by paper, forelectrolytic facsimile recording, alternative procedures are available.These may be listed as involving the following thre methods: (a)chemical treatment of paper at the recorder, (12) damp pre-treated paperrequirin no treatment at the recorder, and (0) dry pro-treated paperrequiring treatment with water at the recorder.

Considering the recorder-treated paper, the untreated paper is fedthrough an immersion bath or over wet rollers, where. it becomessaturated with a solution of the recording chemicals. After removal ofexcess solution by doctor blades, and of excess moisture, by naturalevaporation or by a heated roller, the wet paper passes through thefacsimile recording mechanism. This method has been the one mostcommonly used in this laboratory, as it is more convenientexperimentally, since both recording and paper treatment are combined inone operation. It has the advantage of lower cost for chemicals andpaper due to elimination of pretreating costs, and is excellent for usein commercial high speed recording where properly instructed operatorsgive the recorders frequent attention. It may not be entirely suitablefor home reception of facsimile broadcasting, since it involves thehandling in the home of chemicals which require an element of care andprecaution to avoid spilling, discoloring of furniture and clothes.

With respect to the damp ore-treated paper (1)), the treating andrecording operation may be separated, the paper being treated andrewound while still wet, and delivered in sealed moistureproofcontainers to the recorders. When required for use, the wet roll ofpaper is transferred to a slot-ted container in a recorder, from whichit is fed to the printing mechanism. This method imposes less strain onthe paper than any other wet electrolytic recording method, as the damppaper does not stretch or wrinkle between the slot and the printingpoint. Consequently much weaker paper may be used. Quick starting withintermittent operation, a desirable feature in telegraph offices, iseasily accomplished by manually pulling out the paper for a distanceequal to that between thecontainer slot and the printing point. Theinclusion of wetting agents in the treating solution eliminatesexcessive drying of the paper between the container slot and theprinting point during normal operation.

The shelf life of damp treated paper varies with the chemicals used andwith the alkalinity; usually, the interval within which it should beutilized extends for slightly less than three months from the time thatthe paper has been prepared. Refrigeration, even with dry ice, does notharm either the chemicals or the paper and desirably functions toincrease the shelf life. A temperature just above the freezing point ofwater has shown indications of providing the best results, and avoidsthe necessity for thawing the paper before use.

Both metal foil wrappers and tin cans with or without internal coatinghave been utilized for packaging damp pretreated paper in the case ofthe cans. a tendency toward rusting is manifested, and for this reasonthe metal foil is preferable. Tin foil gives better results than eitherlead or aluminum foil, but it is believed that the moisture retentionmay not be as effective as in the case of a sealed metal can. Theacidity of asphalt-laminated paper causes discoloration of the outerlayers of the pre-treated paper. Preferred results may be obtainable byuse of a metal foil wrapper-on the treated roll of paper, together witha waxed fiber can, desirably with a screw top that is waxed after beingclosed.

It is not intended to be restricted to any special procedure withrespect to the application of the reagents to the paper prior to windingthe same for storage. The immersion time may be comparatively short inView of the fact that penetration continues even after the roll isrewound, and with rapid paper travel sufficient solution adheres to thesurface to insure adequate penetration afterward. As an advantageousexpedient, the reagents may be supplied by rollers, coating one side ofthe paper with the dye intermediates and the other with the electrolyte,distributing the other ingredients between the two solutions utilized.In this Way, salt insoluble intermediates may be used, extending thecolor range. This method of application may improve the characteristicof background permanence, since any tendency toward darkening will bemanifested only on one side of the sheet, thereby providing a lighterbackground especially where the paper carrier is semi-translucent.

In the case of dry pre-treated paper, the paper is supplied with thechemicals from a solution and dried before being rewound into rolls. Theapplication of water or other suitable liquid at the recorder is allthat is essential to render the paper susceptible to recording. Thisobviates the paper storage problem, since rolls of dry pre-treated paperretain their white backgrounds very satisfactorily, in some cases thebackground being unaffected for as much as three years.

Where ,wetting agents are resorted to .in the 17 treating solution, therate of penetration of water into dry pretreated paper becomes morerapid than that of solution into untreated paper. Proper Spreadersshould be utilized to remove paper wrinkles formed as a result ofstretching after water is applied, unless the distance from the wettingroller or trough to the printing point is great enough for the paper toflatten out.

For dry pre-treated paper, the treating solution is desirably morehighly concentrated than in the case of recorder-treated paper. Awetting agent concentration of 1.5 grams per liter of solution isdesirable if water is applied only to one side of the paper by means ofa roller, in order to attain penetration through the paper to the otherside. Doubling the dye chemicals (0.05, 0.10 and 0.03 mol per liter ofsolution of amine, nitrite, and coupling compound instead of the 0.025,0.05, and 0.015 mol usually used for recorder-treated paper) greatlyincreases the contrast and color intensity of recordings on drypre-treated paper, as distinguished from the case of recorder-treatedpaper where substantial increase in concentration may provide only aslight beneficial effect. The electrolyte concentration of approximatelytwo-thirds of a mol per liter of solution, which is used forrecordertreated paper, similarly is quite satisfactory for drypre-treated paper.

' The packaging problem is much simpler than with wet pre-treated paper.An acid-free wrapper in contact with the paper, with an outerasphalt-laminated moisture-proof paper is adequate for storage purposes,

As in the case of preparing the damp paper, it 3 may be advantageous tocoat part of the ingredients on one side of the paper and the remainderon the other, in order to improve background permanence and permit theuse of mutually insoluble ingredients. The problem of large scaleproduction of treating paper remains to be solved. .,Another, or dryelectric method, involves the use vof paper that is electricallyconductive when dry and is also coated with dry chemicals which undergoa color change upon being subjected to an electric current.

In accordance with the above description, it will be apparent thatsheets of the carrier material may be impregnated with one or more ofthe various ingredients and solutions within the purview of theinvention, and then permitted to dry. When the carrier is dry, it isessentially nonconducting and is not in proper condition to be operatedupon by the passage of electric current. To utilize the same, it may behumidified or dampened by any appropriate means, such as by steam orwater vapor, in order to increase the conductivity thereof and render itutilizable in the facsimile receiving machine. By so preparing thesheets of chemically treated paper in a dry form as separate rolls, itis possible to use this treated orsensitized paper by merely subjectingthe same to an appropriate degree of moisture in order that the currentmay pass therethrough and accordingly cause a dye to appear thereon,corresponding with the electric impulses from a transmitting source.

i As pointed out hereinabove, the details of the facsimile recorder froma structural standpoint do not constitute an element of the presentinvention. Substantially any facsimile recorder available wherein itsfunctioning is dependent upon electrical impulses emanating from atransmitting source, passing through a conductive carrier materialprovided with ingredients adapted for diazotization and coupling toproduce an azo dye coloration, will satisfy the apparatus requirementsof the present invention. The nature of the electrodes, however, may beof interest, although it is not contemplated that they should be of thetype which enter into the compositions of the dyes formed duringelectrolytic diazotization. Among the contact electrodes which have beenutilized are stainless steel, tungsten, molybdenum, platinuum, andplatinum-irridium. In general, the hard, inert metals such asplatinm-irridium and the stellites provide the best results as recordinganodes. Non-magnetic stainless steels similarly give good results, butthe colors differ from that produced by the platinum or stellite, andmay be less attractive in appearance, possibly attributable tocollateral reactions involving the iron. Stellite, according to HackhsChemical Dictionary, third edition (1944), is an alloy of steel withcobalt and 10 to 50 per cent chromium and/or tungsten, used forhigh-speed tools and instruments. Ordinary steels which are stronglyattracted by magnets do not permit any diazotization reaction, but, onaccasion, they produce a moderately pale green recording which isbelieved to result from oxidation of the intermediates. In the case ofalloy electrodes, the percentage of azo color resulting fromdiazotization appears to increase as the magnetic characteristics of thealloy decrease. By way of explanation as a plausible hypothesis, it maybe that the magnetic metals create a strong magnetic field when thecurrent passes, and this magnetic field orients the electrically chargedions in such directions and in such manner that they preclude thepossibility of diazotization.

Copper alloys and electrodes generally made from copper or nickel tendto inhibit electrolytic diazotization recording and are, therefore, as ageneral matter not satisfactory for use as recording anodes, althoughthey give excellent results as cathodes. In this category is theberylliumcopper alloy. I

Tungsten generally provides satisfactory recordings, but it manifests atendency to buildup a non-conductive coating, thereby requiring moresignal current for effective recording as well as the occasionalnecessity for reversing the current during a brief interval in order toremove the coating.

The tendency is for the cathode to indicate substantially lesselectrolytic wear than the anode, since it is attacked only by nascenthydrogen and by increased alkalinity at the time of current flow. With abar-helix type of recorder, the cathode is desirably in wire form, andthe principal wear is due to abrasion which gradually renders the wireflat. The beryllium-copper cathode necessitates more frequentreplacement than the anode when the latter is either platinum-irridiumor stellite. A cathode helix wire of stellite may out-last severalstellite or platinumirridium anode printer bars.

It will be apparent from the foregoing that the use of compositionswithin the scope of the present disclosure enables the production ofdyes and pigments by subjecting solutions or mixtures of chemicals toelectric current. Such dyes or pigments may be obtained in the form of apaste, powder, or as a liquid solution, and subsequently adapted for useas coloring paints, inks, etc., or for dyeing various materials. It iswithin the contemplation of the invention to produce such dyes orpigments by intermittent or continuous reaction. Materials such asclothing, piece goods,

yarn, paper, and generally any'fibrous 'material susceptible'to dyes,and particularly azodyes,"fa'll within the purview of the presentdisclosure. They may be treated by immersion in a container filled witha solution of predetermined ingredients and subsequently subjecting suchsolution to the flow of an electric current in order that the dye may befixed in or on the materials immersed therein; thus, the dye applicationmay be in the form of a surface coating or a dyeing within the fibrousstructure. Definitely contemplated 'is the formation of the dye in situ.

As'a significant feature of the invention, the preparation of a carriersurface or material in a manner to render it subject to diazotizationand azo dye formation upon the passing of a current therethrough, as infacsimile recording, is described herein. In accordance with the presentdisclosure, a uniform color concentration, dependent upon the electricalimpulses which motivatethe electrolytic action, as for example, thecurrent which passes to the facsimile recorder from a transmittingsource, is attained. Moreover, the invention enables a regulation andcontrol of the reaction in a manner to prevent premature dye formation,and this is particularly applicable to facsimile recording, since itmakes possible a precision commensurate with the vastly increased rateof recordation which'is possible by an effective electrolytic reaction.Many other advantages are similarly attributable tothe invention as willbe apparent from a consideration of the above description of the manydetails and ramifications which have been presented.

While I have described my invention in accordance with preferredembodiments as to compositions, articles of manufacture, and procedure,it is apparent that many variations and modifications both as toprocedural details, compositions of matter, and articles of manufacturemay be made without departing from the scope of equivalents within thepurview and spirit'of the invention;

The term facsimile as used herein is intended to involve not only thereproduction on the recording material of a pre-existing subject, forexample a photograph which is scanned and reproduced in. accordance withthe impulses emanating from the scanning operation, but also embracesthe recording of subject matter in the 'process of creation or formationwithout a physically preexisting subject. As illustrative of this lattercategory would be the recording of simply a mental preconception, forexample a pattern or design, either of a single color and shadesthereof, or multicolors, which is recorded in accordance with anappropriate manual or automatic variation of the electric impulsesdelivered to the electrodes. Similarly in this category is intended therecording of an arbitrary or haphazard design, pattern or other subject,for example one secured by haphazardly or arbitrarily varying electricimpulses delivered to the electrode by punching keys on a masterkeyboard having suitable electrical connections, by manually or autmatically varying resistance. or the like.

What is claimed is:

1. A fibrous sheet material for the electrolytic formation of an azodyestufif thereon carrying a dyestuff-forming composition comprising adiazotizable heterocyclic amine selected from the class consisting ofaminoquinolines, aminopyridines and aminopyrimidines, a sufficientquantity of an ionizable nitrite -to 'produce'th'e nitrite ionsnecessary for diazotization of said amine under the influence of theelectrolyzing current, a'watersoluble, inorganic salt as the electrolytein an amount to insure passage of the electrolyzing current, .asuflicient quantity of an azo dye coupling component to couple with thediazonium compound when formed to produce an azo dye and a quantity ofalkali sufficient to impart to said composition a pH on the alkalineside to thereby preclude diazonium salt formation until the fibroussheet material is subjected to the action of the 'electrolyzing current.

2. The article as defined in claim 1 wherein the heterocyclic amine isan amino pyridine.

3. The article as defined in claim .1 wherein the heterocyclic amine is2.6-diaminopyridine.

4. The article as defined in claim 1 wherein the coupling component is acompound having an active methylen group.

5. The article as defined in claim 1 wherein the coupling component is aphenol.

6. The article as defined in claim 1 wherein the composition contains awetting agent to facilitate the application of the composition to thefibrous sheet material.

7. The article as defined in claim 1 in which the composition containsa, compound 'to improve the color intensity of the'azo dyes, saidcompound being selected from the class consisting of urea, thiourea anddicy'an'diamidine.

NELLIE W. SOLOMON, Administratrir of the Estate of Myer Solomon,

Deceased.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 168,466 Edison Oct. 5, 1875761,310 'Loeb May 31, 1904 1,844,199 Bicknell et al. Feb. 9,19321,880,449 Hickman et al. Oct. 4, 1932 1,892,099 Cornell Dec. '27, 19321,916,947 Haendel July 4, 1933 1,970,539 Bausch 1 Aug. 31, 19342,063,992 Elsey .Dec. 15, 1936 2,108,852 Gettinger Feb. 22, 19382,173,141 'Talmey Sept. 19, 1939 2,181,533 Kline et a1. Nov. 28, 1939,306, 7 Solomon Dec. 29, 1942 2,148,910 Mietzsch et al Feb. 28, 19392,283,220 McNally et a1 May 19, 1942 2,192,127 Ebel et a1 Feb. 27, 19401,886,480 Haller et a1 NOV. 8, 1932 FOREIGN PATENTS Number Country Date489,429 British July 25, 1938 OTHER REFERENCES Journal Chem. Soc.(London), vol. 97, 1910, pages 1337-1347. (Copy in the Patent OfliceLibrary.)

The Aromatic Diazo Compounds, by Saunders, 1936, pages 1-8, 67-74,102-108. (Copy in Division 43 of the Patent Ofiice.)

Websters New International Dictionary, 2nd edition, 1940, page 2468.(Copy in the Patent Ofilce Library.)

